The present invention relates to an optical system adapted to be disposed between a source capable of emitting a beam of light and a target.
The invention is more particularly, but not exclusively, applicable to a surgical apparatus for modifying the curvature of the cornea.
Among the different known techniques for surgically treating certain disorders, such as myopia and hypermetropia, by modifying the curvature of the cornea, the elimination of corneal matter by photodecomposition by means of a beam of ultraviolet light produced by a laser source, in particular an excimer laser, is the most recent technique to have been envisaged.
An optical system, comprising in particular focussing optics, is disposed between the laser source and the eye, which system directs the beam onto the zone of cornea to be eliminated and forms a light spot on a part of said zone, said spot being capable of scanning the whole of said cornea zone.
However, due to characteristics inherent therein, the beam generated by the laser source is not always stigmatic, i.e. it sometimes presents, in the image focus of focussing optics, a section of oblong shape and not a circular "punctual" or quasi-punctual section. In this way, a light spot, maintaining a symmetry of revolution, i.e. which remains circular or virtually circular, cannot be obtained on the target, in the present case an eye, when said target is displaced relatively to said optics in the image space of the latter, which relative displacement is necessary to allow scanning by said light spot of the whole of the cornea zone to be eliminated.